This invention relates to a non-chokable pump comprising an impeller which has blades for delivering solids-containing media.
Such non-chokable pumps are also referred to as vortex pumps, the delivery power of which is transferred from a rotating plate provided with blades, the so-called non-chokable impeller, to the flow medium. Non-chokable impellers are particularly suitable for delivering media mixed with solid additions, such as for example dirty water. The non-chokable impeller is a radial impeller which has a large passage for the solids contained in the delivery medium and has a low susceptibility to faults.
A non-chokable pump for delivering liquids mixed with solid additions is described in WO 2004/065796 A1. There is a spacing between the impeller and the suction-side casing wall, in order that solid bodies can pass through the non-chokable pump without blockages. The transition from the suction-side casing wall to the wall of the casing space, which space is situated radially with respect to the impeller, is realized smoothly. The casing space is of asymmetric design.
A non-chokable pump whose impeller consists of a support plate equipped with open blades is described in EP 1 616 100 B1. The blades have different heights. A suction-side casing wall runs conically. The spacing of the casing wall to the front edges of the relatively high blades of the impeller decreases with diameter. A passage with a minimum extent follows a front edge of a blade of relatively low height, which blade is inclined toward the impeller outlet, in a constant manner.
Referred to as a ball passage is a free, non-constricted impeller passage. It describes the largest permissible diameter of the solids for ensuring a blockage-free passage. It is specified as a ball diameter in millimeters. The ball passage corresponds, at most, to the nominal width of the suction or discharge connector. In order that this maximum possible ball passage is achieved in conventional non-chokable pumps, it is also necessary that, inside the casing, the spacing of the blade front to the suction-side casing wall likewise corresponds to at least the nominal width of the suction or discharge connector.
If the bladeless space between the blade front and the opposite casing wall exceeds a certain dimension, the efficiency of the non-chokable pump is reduced. The larger the spacing between the impeller and the suction-side casing wall, the lower the efficiency of the non-chokable pump.
It is the object of the invention to specify a non-chokable pump which is able to deliver media even having relatively large solids and which has at the same time a highest possible efficiency according to the design. The non-chokable pump should be characterized by a production method which is as cost-effective as possible and ensure a long lifetime. Moreover, the non-chokable pump should be usable in as versatile a manner as possible and have low susceptibility to faults and have a favorable NPSH value. Cavitation damage should be avoided.
According to the invention, the blades are arranged in bundles on the non-chokable impeller. In this case, the spacing of the blades within the bundles is smaller than the spacing of the bundles to one another.
Due to the construction according to the invention, a sufficient ball passage together with high delivery efficiency of the pump is ensured.
The arrangement in bundles of the blades on the support plate allows the spacing between the inlet-side casing wall and the blade front to be reduced and at the same time a sufficient ball passage to still be ensured.
Since the spacings between the bundles are larger than the spacings of the blades in the bundles, a sufficiently large ball passage is ensured even for the case where the spacing of the blade front of the impeller is smaller than the inner diameter of the suction connector or discharge connector. As a result, blockages are avoided and at the same time high efficiency during delivery is ensured. The bundled arrangement of the blades allows the spacing of the impeller to the suction-side casing wall to be reduced without blockages occurring. The efficiency of the non-chokable pump is consequently increased.
Preferably, the spacing of the blade front of the impeller is less than 90%, in particular less than 80%, of the diameter of the suction mouth or the inner diameter of the suction connector.
Each bundle comprises at least two blades. Bundles with in each case two or three blades prove to be particularly favorable. In a variant of the invention, each bundle comprises four blades.
The support plate of the non-chokable impeller has a hub projection which is formed toward the suction side and on which the blades act. The blades project from the support plate in the suction-side direction and have a profile which is curved opposite to the rotational direction. Here, all the blades may have the same curvature. In an alternative variant, the blades have different curvatures. It is thus possible, for example, for blades with different curvatures to be arranged within a bundle.
Expediently, the spacing of the blades in the bundles is less than 90%, preferably less than 80%, in particular less than 70%, of the spacing of the bundles to one another.
In a particularly advantageous embodiment of the invention, the non-chokable impeller comprises two bundles of blades, which bundles are preferably arranged so as to be offset from one another by 180°. In this case, it proves to be favorable if each bundle comprises the same number of blades.
The spacings of the blades within the bundles and/or the spacings of the bundles to one another are preferably specified as angles of the blade separation. According to the invention, the angles of the blade separation within the bundles are smaller than the angles of the blade separation between the bundles.
Expediently, the angles of the blade separation between the bundles are more than 60°, preferably more than 70°, in particular more than 80°.
It proves to be favorable if the angles of the blade separation within the bundles are less than 70°, preferably less than 60°, in particular less than 50°.
In a particularly favorable embodiment of the invention, the impeller is formed integrally with the blades. Here, it proves to be favorable if the impeller and/or the blades are produced from a metallic material. Preferably, a cast material is used in this case.
In a variant of the invention, the angles of the blade separation between the bundles are not an integer multiple of the angles of the blade separation within the bundles, and so the arrangement in bundles does not stem from an impeller with blades of equal angular separation in which individual blades are omitted.
In a particularly favorable variant of the invention, the height of the blades decreases, in relation to a reference plane, in the radial direction. The decrease preferably occurs at a bevel angle of more than 2°, in particular more than 3°. It proves to be favorable if the decrease in the height of the blades occurs at a bevel angle of less than 8°, in particular less than 7°.
Further features and advantages of the invention will emerge from the description of exemplary embodiments on the basis of drawings, and from the drawings themselves.